Semiconductor devices and methods of manufacturing thereof

ABSTRACT

A semiconductor device includes a first transistor, a second transistor, a third transistor, and a fourth transistor. The first and second transistors operate under a lower gate voltage than the third and fourth transistors. The first transistor has a first active gate structure and the second transistor has a second active gate structure. The first and second active gate structures are separated by a first gate isolation structure along a first direction. The third transistor has a third active gate structure and the fourth transistor has a fourth active gate structure. The third and fourth active gate structures are separated by a second gate isolation structure along the first direction. The variation of a first distance between respective sidewalls of the first gate isolation structure is equal to the variation of a second distance between respective sidewalls of the second gate isolation structure along the first direction.

BACKGROUND

The present disclosure generally relates to semiconductor devices, andparticularly to methods of making a non-planar transistor device.

The semiconductor industry has experienced rapid growth due tocontinuous improvements in the integration density of a variety ofelectronic components (e.g., transistors, diodes, resistors, capacitors,etc.). For the most part, this improvement in integration density hascome from repeated reductions in minimum feature size, which allows morecomponents to be integrated into a given area.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a perspective view of a Fin Field-Effect Transistor(FinFET) device, in accordance with some embodiments.

FIG. 2 illustrates a flow chart of an example method for making anon-planar transistor device, in accordance with some embodiments.

FIGS. 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14A, 14B, 14C, 14D, 15A, 15B,15C, 15D, 16A, 16B, 16C, and 16D illustrate cross-sectional views of anexample FinFET device (or a portion of the example FinFET device) duringvarious fabrication stages, made by the method of FIG. 2, in accordancewith some embodiments.

FIGS. 17A, 17B, and 17C illustrate top views of the example FinFETdevice (or a portion of the example FinFET device) during a certainfabrication stage, made by the method of FIG. 2, in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments of the present disclosure are discussed in the context offorming a FinFET device, and in particular, in the context of forming areplacement gate of a FinFET device. In some embodiments, a dummy gatestructure is formed over a number of fins. The fins can include one ormore active fins and one or more dummy fins. Hereinafter, the term“active fin” is referred to as a fin that will be adopted as an activechannel to electrically conduct current in a finished semiconductordevice (e.g., FinFET device 300 shown below), when appropriatelyconfigured and powered; and the term “dummy fin” is referred to as a finthat will not be adopted as an active channel (i.e., a dummy channel) toelectrically conduct current in a finished semiconductor device (e.g.,FinFET device 300 shown below). Next, gate spacers are formed around thedummy gate structure. After an interlayer dielectric (ILD) layer isformed around the gate spacers to overlay respective portions of thefins, a portion of the dummy gate structure over the at least one dummyfin is removed to form a gate cut trench. In various embodiments, awidth of the gate cut trench is not necessarily in proportion (e.g.,less than) to a width of the dummy fin. Next, such a gate cut trench isfilled with a gate isolation structure. Next, the remaining portion ofthe dummy gate structure is replaced with an active gate structure,which can include one or more metal gate layers.

Metal gate layers over multiple fins formed by the above describedmethod can provide various advantages in advanced processing nodes. Thegate isolation structure is formed over the dummy fin to disconnect,intercept, cut, or otherwise separate the metal gate layers. Forming thegate isolation structure to cut metal gate layers can allow differentportions of the metal gate layers to be electrically coupled torespective active fin(s).

In certain areas over a substrate, the active fins may be relativelysparsely disposed, which results in the dummy fin formed in these areashaving a greater width; and in certain areas over the substrate, theactive fins may be relatively densely disposed, which results in thedummy fins formed in these areas having a less width. The criticaldimension (e.g., the width) of a gate cut trench formed by the existingtechnologies is typically proportional to the width of a dummy finexposed by the gate cut trench, which causes various issues. Forexample, when forming the gate cut trenches over these different areas,the wider gate cut trench may not be successfully formed (e.g., withresidual dummy gate structure left on the dummy fin). Accordingly, themetal gate layer cannot be successfully cut (isolated) by a gateisolation structure filling the gate cut trench.

The present disclosure provides various embodiments of semiconductordevices and the method of forming the same that address such issues. Invarious embodiments, over a substrate, some of the dummy fins are formedwider, and some of the dummy fins are formed narrower. Based on a widthof the wider dummy fin, the width of a gate cut trench can beselectively formed to be in proportion or out of proportion to the widthof the wider dummy fin. For example, when the width of the wider dummyfin is determined to be greater than a predefined threshold, the gatecut trench may be formed to be out of proportion to (e.g., less than)the width of the dummy fin. On the other hand, when the width of thewider dummy fin is determined to be equal to or less than the predefinedthreshold, the gate cut trench may be formed to be in proportion to thewidth of the dummy fin. In this way, respective gate cut trenches overthe dummy fins having different dimensions can be concurrently formed,while significantly limiting the issues that the existing technologiesare facing.

FIG. 1 illustrates a perspective view of an example FinFET device 100,in accordance with various embodiments. The FinFET device 100 includes asubstrate 102 and a fin 104 protruding above the substrate 102.Isolation regions 106 are formed on opposing sides of the fin 104, withthe fin 104 protruding above the isolation regions 106. A gatedielectric 108 is along sidewalls and over a top surface of the fin 104,and a gate 110 is over the gate dielectric 108. Source region 112S anddrain region 112D are in (or extended from) the fin 104 and on opposingsides of the gate dielectric 108 and the gate 110. FIG. 1 is provided asa reference to illustrate a number of cross-sections in subsequentfigures. For example, cross-section B-B extends along a longitudinalaxis of the gate 110 of the FinFET device 100. Cross-section A-A isperpendicular to cross-section B-B and is along a longitudinal axis ofthe fin 104 and in a direction of, for example, a current flow betweenthe source/drain regions 112S/112D. Subsequent figures refer to thesereference cross-sections for clarity.

FIG. 2 illustrates a flowchart of a method 200 to form a non-planartransistor device, according to one or more embodiments of the presentdisclosure. For example, at least some of the operations (or steps) ofthe method 200 can be used to form a FinFET device (e.g., FinFET device100), a nanosheet transistor device, a nanowire transistor device, avertical transistor device, a gate-all-around (GAA) transistor device,or the like. It is noted that the method 200 is merely an example, andis not intended to limit the present disclosure. Accordingly, it isunderstood that additional operations may be provided before, during,and after the method 200 of FIG. 2, and that some other operations mayonly be briefly described herein. In some embodiments, operations of themethod 200 may be associated with cross-sectional views of an exampleFinFET device at various fabrication stages as shown in FIGS. 3, 4, 5,6, 7, 8, 9, 10, 11, 12, 13, 14A, 14B, 14C, 14D, 15A, 15B, 15C, 15D, 16A,16B, 16C, and 16D, respectively, which will be discussed in furtherdetail below.

In brief overview, the method 200 starts with operation 202 of providinga substrate. The method 200 continues to operation 204 of forming activefins. The method 200 continues to operation 206 of forming dummy fins.The method 200 continues to operation 208 of forming isolation regions.The method 200 continues to operation 210 of forming dummy gatestructures over the fins. The method 200 continues to operation 212 offorming gate spacers. The method 200 continues to operation 214 ofgrowing source/drain structures. The method 200 continues to operation216 of forming an interlayer dielectric (ILD). The method 200 continuesto operation 218 of cutting the dummy gate structures. The method 200continues to operation 220 of forming gate isolation structures. Themethod 200 continues to operation 222 of forming active gate structures.

As mentioned above, FIGS. 3-16D each illustrate, in a cross-sectionalview, a portion of a FinFET device 300 at various fabrication stages ofthe method 200 of FIG. 2. The FinFET device 300 is similar to the FinFETdevice 100 shown in FIG. 1, but with multiple fins. For example, FIGS.3-10 and 14A-16D illustrate cross-sectional views of the FinFET device300 along cross-section B-B (as indicated in FIG. 1); and FIGS. 11-13illustrate cross-sectional views of the FinFET device 300 alongcross-section A-A (as indicated in FIG. 1). Although FIGS. 3-16Dillustrate the FinFET device 300, it is understood the FinFET device 300may include a number of other devices such as inductors, fuses,capacitors, coils, etc., which are not shown in FIGS. 3-16D, forpurposes of clarity of illustration.

Corresponding to operation 202 of FIG. 2, FIG. 3 is a cross-sectionalview of the FinFET device 300 including a semiconductor substrate 302 atone of the various stages of fabrication. The cross-sectional view ofFIG. 3 is cut along the lengthwise direction of an active/dummy gatestructure of the FinFET device 300 (e.g., cross-section B-B indicated inFIG. 1).

The substrate 302 may be a semiconductor substrate, such as a bulksemiconductor, a semiconductor-on-insulator (SOI) substrate, or thelike, which may be doped (e.g., with a p-type or an n-type dopant) orundoped. The substrate 302 may be a wafer, such as a silicon wafer.Generally, an SOI substrate includes a layer of a semiconductor materialformed on an insulator layer. The insulator layer may be, for example, aburied oxide (BOX) layer, a silicon oxide layer, or the like. Theinsulator layer is provided on a substrate, typically a silicon or glasssubstrate. Other substrates, such as a multi-layered or gradientsubstrate may also be used. In some embodiments, the semiconductormaterial of the substrate 302 may include silicon; germanium; a compoundsemiconductor including silicon carbide, gallium arsenic, galliumphosphide, indium phosphide, indium arsenide, and/or indium antimonide;an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs,GaInP, and/or GaInAsP, or combinations thereof.

In some embodiments, the FinFET device 300 can include areas 302A and302B. The area 302A can be configured to form a number of input/output(I/O) transistors (hereinafter “I/O area 302A”); and the area 302B canbe configured to form a number of core transistors (hereinafter “corearea 302B”). The terms “I/O transistor” and “core transistor,” as usedherein, may be generally referred to a transistor configured to operateunder a relatively higher voltage (e.g., higher V_(gs)) and a transistorconfigured to operate under a relatively lower voltage (e.g., lowerV_(gs)), respectively. Thus, it should be understood that the I/Otransistor can include any of various other transistors operating undera relatively higher voltage and the core transistor can include any ofvarious other transistors operating under a relatively lower voltage,while remaining within the scope of the present disclosure. The I/Otransistor, when appropriately configured, may have a relatively thickergate dielectric; and the core transistor, when appropriately configured,has a relatively thinner gate dielectric. Further, the I/O transistorsmay be formed in a first area of the substrate (e.g., I/O area 302A)with a relatively lower density of transistors; and the core transistorsmay be formed in a second area of the substrate (e.g., core area 302B)with a relatively higher density of transistors. As such, features(e.g., fins) in the I/O area 302A may be more sparsely formed, whencompared to the features (e.g., fins) formed in the core area 302B.

As shown in FIG. 3 (and the following figures), the I/O area 302A andcore area 302B are separated from each other by a divider 303, which caninclude additional features/components/devices that are omitted forsimplicity. It should be appreciated that some of the operations of themethod 200 may be concurrently performed in the I/O area 302A and corearea 302B. For purposes of illustration, some of the feature(s) formedin the I/O area 302A and the core area 302B are hereinafter shown in thesame figure that corresponds to one of the operations of the method 200.

Corresponding to operation 204 of FIG. 2, FIG. 4 is a cross-sectionalview of the FinFET device 300 including semiconductor fins 404A, 404B,404C, and 404D at one of the various stages of fabrication. Thecross-sectional view of FIG. 4 is cut along the lengthwise direction ofan active/dummy gate structure of the FinFET device 300 (e.g.,cross-section B-B indicated in FIG. 1).

The semiconductor fins 404A-B are formed in the I/O area 302A, and thesemiconductor fins 404C-D are formed in the core area 302B. Although twosemiconductor fins are shown in each of the I/O area 302A and core area302B, it should be appreciated that the FinFET device 300 can includeany number of semiconductor fins in each of the areas 302A and 302Bwhile remaining within the scope of the present disclosure.

The semiconductor fins 404A-D may be each configured as an active fin,which will be adopted as an active (e.g., electrically functional) finor channel in a completed FinFET. Further, the semiconductor fin 404Amay be configured as the active channel of a first input/output (I/O)transistor of the FinFET device 300 (sometimes referred to as “activeI/O fin 404A”); the semiconductor fin 404B may be configured as theactive channel of a second input/output (I/O) transistor of the FinFETdevice 300 (sometimes referred to as “active I/O fin 404B”); thesemiconductor fin 404C may be configured as the active channel of afirst core transistor of the FinFET device 300 (sometimes referred to as“active core fin 404C”); and the fin 404D may be configured as theactive channel of a second core transistor of the FinFET device 300(sometimes referred to as “active core fin 404D”).

The semiconductor fins 404A-D are formed by patterning the substrate 302using, for example, photolithography and etching techniques. Forexample, a mask layer, such as a pad oxide layer 406 and an overlyingpad nitride layer 408, is formed over the substrate 302. The pad oxidelayer 406 may be a thin film comprising silicon oxide formed, forexample, using a thermal oxidation process. The pad oxide layer 406 mayact as an adhesion layer between the substrate 302 and the overlying padnitride layer 408. In some embodiments, the pad nitride layer 408 isformed of silicon nitride, silicon oxynitride, silicon carbonitride, thelike, or combinations thereof. Although only one pad nitride layer 408is illustrated, a multilayer structure (e.g., a layer of silicon oxideon a layer of silicon nitride) may be formed as the pad nitride layer408. The pad nitride layer 408 may be formed using low-pressure chemicalvapor deposition (LPCVD) or plasma enhanced chemical vapor deposition(PECVD), for example.

The mask layer may be patterned using photolithography techniques.Generally, photolithography techniques utilize a photoresist material(not shown) that is deposited, irradiated (exposed), and developed toremove a portion of the photoresist material. The remaining photoresistmaterial protects the underlying material, such as the mask layer inthis example, from subsequent processing steps, such as etching. Forexample, the photoresist material is used to pattern the pad oxide layer406 and pad nitride layer 408 to form a patterned mask 410, asillustrated in FIG. 4.

The patterned mask 410 is subsequently used to pattern exposed portionsof the substrate 302 to form trenches (or openings) 411, therebydefining the active fins 404A-D between adjacent trenches 411 asillustrated in FIG. 4. When multiple fins are formed, such a trench maybe disposed between any adjacent ones of the fins. In some embodiments,the active fins 404A-D are formed by etching trenches in the substrate302 using, for example, reactive ion etch (ME), neutral beam etch (NBE),the like, or combinations thereof. The etch may be anisotropic. In someembodiments, the trenches 411 may be strips (viewed from the top)parallel to each other, and closely spaced with respect to each other.In some embodiments, the trenches 411 may be continuous and surround theactive fins 404A-D.

The active fins 404A-D may be patterned by any suitable method. Forexample, the active fins 404A-D may be patterned using one or morephotolithography processes, including double-patterning ormulti-patterning processes. Generally, double-patterning ormulti-patterning processes combine photolithography and self-alignedprocesses, allowing patterns to be created that have, for example,pitches smaller than what is otherwise obtainable using a single, directphotolithography process. For example, in one embodiment, a sacrificiallayer is formed over a substrate and patterned using a photolithographyprocess. Spacers are formed alongside the patterned sacrificial layerusing a self-aligned process. The sacrificial layer is then removed, andthe remaining spacers, or mandrels, may then be used to pattern the fin.

As shown in FIG. 4, the active fins 404A-B in the I/O area 302A areformed to be separated from each other with a first spacing 417, and theactive fins 404C-D in the core area 302B are formed to be separated fromeach other with a second spacing 419. In various embodiments, the firstspacing 417 can be substantially greater than the second spacing 419.For example with a certain process node (e.g., 5 nanometers (nm)), thefirst spacing 417 can range from about 5 nanometers to about 500nanometers, and the second spacing 419 can range from about 5 nanometersto about 500 nanometers.

FIGS. 3 and 4 illustrate an embodiment of forming the active fins404A-D, but a fin may be formed in various different processes. Forexample, a top portion of the substrate 302 may be replaced by asuitable material, such as an epitaxial material suitable for anintended type (e.g., N-type or P-type) of semiconductor devices to beformed. Thereafter, the substrate 302, with epitaxial material on top,is patterned to form the active fins 404A-D that include the epitaxialmaterial.

As another example, a dielectric layer can be formed over a top surfaceof a substrate; trenches can be etched through the dielectric layer;homoepitaxial structures can be epitaxially grown in the trenches; andthe dielectric layer can be recessed such that the homoepitaxialstructures protrude from the dielectric layer to form one or more fins.

In yet another example, a dielectric layer can be formed over a topsurface of a substrate; trenches can be etched through the dielectriclayer; heteroepitaxial structures can be epitaxially grown in thetrenches using a material different from the substrate; and thedielectric layer can be recessed such that the heteroepitaxialstructures protrude from the dielectric layer to form one or more fins.

In embodiments where epitaxial material(s) or epitaxial structures(e.g., the heteroepitaxial structures or the homoepitaxial structures)are grown, the grown material(s) or structures may be in situ dopedduring growth, which may obviate prior and subsequent implantationsalthough in situ and implantation doping may be used together. Stillfurther, it may be advantageous to epitaxially grow a material in anNMOS region different from the material in a PMOS region. In variousembodiments, the active fins 404A-D may include silicon germanium(Si_(x)Ge_(1-x), where x can be between 0 and 1), silicon carbide, pureor pure germanium, a III-V compound semiconductor, a II-VI compoundsemiconductor, or the like. For example, the available materials forforming III-V compound semiconductor include, but are not limited to,InAs, AlAs, GaAs, InP, GaN, InGaAs, InAlAs, GaSb, AlSb, AlP, GaP, andthe like.

Corresponding to operation 206 of FIG. 2, FIG. 5 is a cross-sectionalview of the FinFET device 300 including a dummy channel layer 500 at oneof the various stages of fabrication at one of the various stages offabrication, and FIG. 6 is a cross-sectional views of the FinFET device300 including dummy fins 600A and 600B at one of the various stages offabrication. The cross-sectional views of FIGS. 5 and 6 are each cutalong the lengthwise direction of an active/dummy gate structure of theFinFET device 300 (e.g., cross-section B-B indicated in FIG. 1).

Although the dummy channel layer 500 is shown as being universallydeposited over both of the areas 302A and 302B, it should be understoodthat similar dummy channel layers may be deposited over the I/O area302A and the core area 302B, respectively.

In some embodiments, the dummy channel layer 500 can include adielectric material used to form the dummy fins 600A-B. For example, thedielectric material may include silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon carbonitride, siliconoxycarbonitride, silicon oxycarbide, or combinations thereof. In anotherexample, the dielectric material may include group IV-based oxide orgroup IV-based nitride, e.g., tantalum nitride, tantalum oxide, hafniumoxide, or combinations thereof. The dummy channel layer 500 may beformed using low-pressure chemical vapor deposition (LPCVD) or plasmaenhanced chemical vapor deposition (PECVD), for example.

Upon depositing the dummy channel layer 500 overlaying the active fins404A-D, one or more dummy fins, e.g., 600A and 600B, may be formedbetween the active fins 404A-D. For example, the dummy fin 600A may beformed between the active fins 404A-B; and the dummy fin 600B may beformed between the active fins 404C-D. The dummy fins 600A-B are formedby patterning the dummy channel layer 500 using, for example,photolithography and etching techniques. For example, a patterned mask(not shown) may be formed over the dummy channel layer 500 to maskportions of the dummy channel layer 500 to form the dummy fins 600A-B.Subsequently, unmasked portions of the dummy channel layer 500 may beetched using, for example, reactive ion etch (RIE), neutral beam etch(NBE), the like, or combinations thereof, thereby defining the dummyfins 600A-B between adjacent active fins 404A-D (or in the trenches 411)as illustrated in FIG. 6. The etch may be anisotropic, in someembodiments. In some other embodiments, the dummy fins 600A-B may beformed concurrently with or subsequently to forming isolation regions(e.g., 700 of FIG. 7) between adjacent fins, which will be discussedbelow.

As illustrated in FIG. 6, the dummy fin 600A formed in the I/O area 302Ahas a width (along a direction perpendicular to a lengthwise directionof the fins) 601A, and the dummy fin 600B formed in the core area 302Bhas a width (along the same direction) 601B. In various embodiments, thewidth 601A is substantially greater than the width 601B. For examplewith a certain process node (e.g., 5 nanometers (nm)), the width 601Acan range from about 2 nanometers to about 200 nanometers, and the width601B can range from about 2 nanometers to about 200 nanometers.

Corresponding to operation 208 of FIG. 2, FIG. 7 is a cross-sectionalview of the FinFET device 300 including isolation regions 700 at one ofthe various stages of fabrication. The cross-sectional view of FIG. 7 iscut along the lengthwise direction of an active/dummy gate structure ofthe FinFET device 300 (e.g., cross-section B-B indicated in FIG. 1).

The isolation regions 700, which are formed of an insulation material,can electrically isolate neighboring fins from each other. Theinsulation material may be an oxide, such as silicon oxide, a nitride,the like, or combinations thereof, and may be formed by a high densityplasma chemical vapor deposition (HDP-CVD), a flowable CVD (FCVD) (e.g.,a CVD-based material deposition in a remote plasma system and postcuring to make it convert to another material, such as an oxide), thelike, or combinations thereof. Other insulation materials and/or otherformation processes may be used. In an example, the insulation materialis silicon oxide formed by a FCVD process. An anneal process may beperformed once the insulation material is formed. A planarizationprocess, such as a chemical mechanical polish (CMP), may remove anyexcess insulation material and form top surfaces of the isolationregions 700 and a top surface of the fins 404A-D and 600A-B that arecoplanar (not shown). The patterned mask 410 (FIG. 4) may also beremoved by the planarization process.

In some embodiments, the isolation regions 700 include a liner, e.g., aliner oxide (not shown), at the interface between each of the isolationregions 700 and the substrate 302 (active fins 404A-D). In someembodiments, the liner oxide is formed to reduce crystalline defects atthe interface between the substrate 302 and the isolation region 700.Similarly, the liner oxide may also be used to reduce crystallinedefects at the interface between the active fins 404A-D and theisolation region 700. The liner oxide (e.g., silicon oxide) may be athermal oxide formed through a thermal oxidation of a surface layer ofthe substrate 302, although other suitable method may also be used toform the liner oxide.

Next, the isolation regions 700 are recessed to form shallow trenchisolation (STI) regions 700, as shown in FIG. 7. The isolation regions700 are recessed such that the upper portions of the fins 404A-D and600A-B protrude from between neighboring STI regions 700. Respective topsurfaces of the STI regions 700 may have a flat surface (asillustrated), a convex surface, a concave surface (such as dishing), orcombinations thereof. The top surfaces of the STI regions 700 may beformed flat, convex, and/or concave by an appropriate etch. Theisolation regions 700 may be recessed using an acceptable etchingprocess, such as one that is selective to the material of the isolationregions 700. For example, a dry etch or a wet etch using dilutehydrofluoric (DHF) acid may be performed to recess the isolation regions700.

As mentioned above, the dummy fins 600A-B may be formed concurrentlywith or subsequently to the formation of the isolation regions 700. Asan example, when forming the active fins 404A-D (FIG. 4), one or moreother active fins may also be formed in the trenches 411. The insulationmaterial of the isolation regions 700 may be deposited over the activefins, followed by a CMP process to planarize the top surfaces of theisolation regions 700 and the active fins, which include the active fins404A-D and the active fins formed in the trenches 411. Subsequently, anupper portion of the active fins formed in the trenches 411 may bepartially removed to form cavities. The cavities are then filled withthe dielectric material of the dummy channel layer 500, followed byanother CMP process to form the dummy fins 600A-B. The isolation regions700 are recessed to form the shallow trench isolation (STI) regions 700,as shown in FIG. 8. Using such a method to form the dummy fins 600A-B,the dummy fins 600A-B are formed on the substrate 302 and a bottomsurface of the dummy fins 600A-B is below the top surface of theisolation regions 700, as shown in FIG. 8. Depending on how much of theisolation regions 700 is recessed, the bottom surface of the dummy fins600A-B may be above the top surface of the isolation regions 700, whileremaining within the scope of the present disclosure.

As another example, after forming the active fins 404A-D (FIG. 4), theinsulation material of the isolation regions 700 may be deposited overthe active fins 404A-D in a controlled deposition rate, thereby causingcavities to be spontaneously formed in the trenches 411. The cavitiesare then filled with the dielectric material of the dummy channel layer500, followed by a CMP process to form the dummy fins 600A-B. Theisolation regions 700 are recessed to form the shallow trench isolation(STI) regions 700, as shown in FIG. 9. Using such a method to form thedummy fins 600A-B, the dummy fins 600A-B are formed on the isolationregions 700 and a bottom surface of the dummy fins 600A-B is embedded inthe corresponding isolation region 700, as shown in FIG. 9. As yetanother example, after forming the active fins 404A-D (FIG. 4) anddepositing the insulation material of the isolation regions 700 over theactive fins 404A-D, a patterned mask may be formed over the isolationregions 700 to expose portions of the isolation regions 700 to form thedummy fins 600A-B (e.g., in the trenches 411). Subsequently, the exposedportions of the isolation regions 700 may be etched using, for example,reactive ion etch (RIE), neutral beam etch (NBE), the like, orcombinations thereof, thereby defining cavities. The cavities are thenfilled with the dielectric material of the dummy channel layer 500,followed by a CMP process to form the dummy fins 600A-B, which issimilar to the illustrated embodiment of FIG. 9.

Corresponding to operation 210 of FIG. 2, FIG. 10 is a cross-sectionalview of the FinFET device 300 including a dummy gate structure 1000 inthe I/O area 302A and a dummy gate structure 1020 in the core area 302Bat one of the various stages of fabrication. The cross-sectional view ofFIG. 10 is cut along a lengthwise direction of the dummy gate structures1000 and 1020 of the FinFET device 300 (e.g., cross-section B-Bindicated in FIG. 1).

The dummy gate structure 1000 is formed to overlay a respective portionof each of the fins (e.g., active fins 400A-B, dummy fin 600A) in thecore area 302B. Prior to, concurrently with, or subsequently to formingthe dummy gate structure 1000 in the I/O area 302A, a dummy gatestructure 1020 may be formed in the core area 302B to overlay a portionof each of the active fins 404C-D, and the dummy fin 600B. The dummygate structure 1020 is similar to the dummy gate structure 1000, exceptfor its dimensions, and thus, the dummy gate structure 1020 will bebriefly discussed below.

The dummy gate structure 1000 includes a dummy gate dielectric 1002 anda dummy gate 1004, in some embodiments. A mask 1006 may be formed overthe dummy gate structure 1000. To form the dummy gate structure 1000, adielectric layer is formed on the active fins 404A-B and dummy fin 600A.The dielectric layer may be, for example, silicon oxide, siliconnitride, silicon oxynitride, silicon carbide, silicon carbonitride,silicon oxycarbonitride, silicon oxycarbide, multilayers thereof, or thelike, and may be deposited or thermally grown. Similarly, the dummy gatestructure 1020 includes a dummy gate dielectric 1022 and a dummy gate1024, with a mask 1026 formed thereon.

A gate layer is formed over the dielectric layer, and a mask layer isformed over the gate layer. The gate layer may be deposited over thedielectric layer and then planarized, such as by a CMP. The mask layermay be deposited over the gate layer. The gate layer may be formed of,for example, polysilicon, although other materials may also be used. Themask layer may be formed of, for example, silicon nitride or the like.

After the layers (e.g., the dielectric layer, the gate layer, and themask layer) are formed, the mask layer may be patterned using suitablelithography and etching techniques to form the mask 1006 (1026). Thepattern of the mask 1006 (1026) then may be transferred to the gatelayer and the dielectric layer by a suitable etching technique to formthe dummy gate 1004 (1024) and the underlying dummy gate dielectric 1002(1022), respectively. The dummy gate 1004 and the dummy gate dielectric1002 cover a respective portion (e.g., a channel region) of each of theactive fins 404A-B and the dummy fin 600A; and the dummy gate 1024 andthe dummy gate dielectric 1022 cover a portion (e.g., a channel region)of the active fins 404C-D and the dummy fin 600B. The dummy gate 1004(1024) may also have a lengthwise direction (e.g., direction B-B ofFIG. 1) perpendicular to the lengthwise direction (e.g., direction ofA-A of FIG. 1) of the fins.

The dummy gate dielectric 1002 is shown to be formed over the activefins 404A-b and the dummy fin 600A (e.g., over the respective topsurfaces and the sidewalls of the fins) and over the STI regions 700 inthe example of FIG. 10. Similarly, the dummy gate dielectric 1022 isformed to overlay the active fins 404C-D and the dummy fin 600B (e.g.,overlaying the respective top surfaces and the sidewalls of the fins).In other embodiments, the dummy gate dielectric 1002 (1022) may beformed by, e.g., thermal oxidization of a material of the fins, andtherefore, may be formed over the fins but not over the STI regions 700.It should be appreciated that these and other variations are stillincluded within the scope of the present disclosure.

FIGS. 11-13 illustrate the cross-sectional views of further processing(or making) of the FinFET device 300 along cross-section A-A of one ofthe active fins 404A-D (as indicated in FIG. 1). As a representativeexample, one dummy gate structures 1000 is illustrated over the activefin 404A in FIGS. 11-13. It should be appreciated that more than onedummy gate structure can be formed over the fin 404A (and each of theother fins, e.g., 404B-D, 600A-B), while remaining within the scope ofthe present disclosure.

Corresponding to operation 212 of FIG. 2, FIG. 11 is a cross-sectionalview of the FinFET device 300 including gate spacer 1100 formed around(e.g., along and contacting the sidewalls of) the dummy gate structure1000. For example, the gate spacer 1100 may be formed on opposingsidewalls of the dummy gate structure 1000. It should be understood thatany number of gate spacers can be formed around the dummy gatestructures 1000 while remaining within the scope of the presentdisclosure.

The gate spacer 1100 may be a low-k spacer and may be formed of asuitable dielectric material, such as silicon oxide, siliconoxycarbonitride, or the like. Any suitable deposition method, such asthermal oxidation, chemical vapor deposition (CVD), or the like, may beused to form the gate spacer 1100. The shapes and formation methods ofthe gate spacer 1100 as illustrated in FIG. 11 are merely non-limitingexamples, and other shapes and formation methods are possible. These andother variations are fully intended to be included within the scope ofthe present disclosure.

Corresponding to operation 214 of FIG. 2, FIG. 12 is a cross-sectionalview of the FinFET device 300 including a number of source/drain regions1200 at one of the various stages of fabrication. The source/drainregions 1200 are formed in recesses of the active fin 404A adjacent tothe dummy gate structures 1000, e.g., between adjacent dummy gatestructures 1000 and/or next to a dummy gate structure 1000. The recessesare formed by, e.g., an anisotropic etching process using the dummy gatestructures 1000 as an etching mask, in some embodiments, although anyother suitable etching process may also be used.

The source/drain regions 1200 are formed by epitaxially growing asemiconductor material in the recess, using suitable methods such asmetal-organic CVD (MOCVD), molecular beam epitaxy (MBE), liquid phaseepitaxy (LPE), vapor phase epitaxy (VPE), selective epitaxial growth(SEG), the like, or a combination thereof.

As illustrated in FIG. 12, the epitaxial source/drain structures 1200may have surfaces raised from respective surfaces of the active fin 404A(e.g. raised above the non-recessed portions of the active fin 404A) andmay have facets. In some embodiments, the source/drain structures 1200of the adjacent fins may merge to form a continuous epitaxialsource/drain structure (not shown). In some embodiments, thesource/drain structures 1200 of the adjacent fins may not merge togetherand remain separate source/drain structures 1200 (not shown). In someembodiments, when the resulting FinFET device is an n-type FinFET, thesource/drain structures 1200 can include silicon carbide (SiC), siliconphosphorous (SiP), phosphorous-doped silicon carbon (SiCP), or the like.In some embodiments, when the resulting FinFET device is a p-typeFinFET, the source/drain structures 1200 comprise SiGe, and a p-typeimpurity such as boron or indium.

The epitaxial source/drain structures 1200 may be implanted with dopantsto form source/drain structures 1200 followed by an annealing process.The implanting process may include forming and patterning masks such asa photoresist to cover the regions of the FinFET device 300 that are tobe protected from the implanting process. The source/drain structures1200 may have an impurity (e.g., dopant) concentration in a range fromabout 1×10¹⁹ cm⁻³ to about 1×10²¹ cm⁻³. P-type impurities, such as boronor indium, may be implanted in the source/drain structures 1200 of aP-type transistor. N-type impurities, such as phosphorous or arsenide,may be implanted in the source/drain structures 1200 of an N-typetransistor. In some embodiments, the epitaxial source/drain structures1200 may be in situ doped during their growth.

Corresponding to operation 216 of FIG. 2, FIG. 13 is a cross-sectionalview of the FinFET device 300 including an interlayer dielectric (ILD)1300 at one of the various stages of fabrication. In some embodiments,prior to forming the ILD 1300, a contact etch stop layer (CESL) 1302 isformed over the structure, as illustrated in FIG. 13. The CESL 1302 canfunction as an etch stop layer in a subsequent etching process, and maycomprise a suitable material such as silicon oxide, silicon nitride,silicon oxynitride, combinations thereof, or the like, and may be formedby a suitable formation method such as CVD, PVD, combinations thereof,or the like.

Next, the ILD 1300 is formed over the CESL 1302 and over the dummy gatestructures 1000. In some embodiments, the ILD 1300 is formed of adielectric material such as silicon oxide, phosphosilicate glass (PSG),borosilicate glass (BSG), boron-doped phosphosilicate Glass (BPSG),undoped silicate glass (USG), or the like, and may be deposited by anysuitable method, such as CVD, PECVD, or FCVD. After the ILD 1300 isformed, an optional dielectric layer 1304 is formed over the ILD 1300.The dielectric layer 1304 can function as a protection layer to preventor reduces the loss of the ILD 1300 in subsequent etching processes. Thedielectric layer 1304 may be formed of a suitable material, such assilicon nitride, silicon carbonitride, or the like, using a suitablemethod such as CVD, PECVD, or FCVD. After the dielectric layer 1304 isformed, a planarization process, such as a CMP process, may be performedto achieve a level upper surface for the dielectric layer 1304. The CMPmay also remove the mask 1006 and portions of the CESL 1302 disposedover the dummy gate 1004 (FIG. 12). After the planarization process, theupper surface of the dielectric layer 1304 is level with the uppersurface of the dummy gate 1004, in some embodiments.

Corresponding to operation 218 of FIG. 2, FIG. 14A is a cross-sectionalview of the FinFET device 300 in which the dummy gate structures 1000and 1020 are respectively cut, intercepted, or otherwise disconnected toform a gate cut trench 1400 in the I/O area 302A and a gate cut trench1450 in the core area 302B at one of the various stages of fabrication.Corresponding to the same operation, FIGS. 14B, 14C, and 14D eachillustrate a cross-sectional view of the FinFET device 300 in which thegate cut trenches 1400 and/or 1450 have different profiles than FIG.14A. The cross-sectional view of FIGS. 14A-D are each cut along thelengthwise direction of the dummy gate structures 1000 and 1020 of theFinFET device 300 (e.g., cross-section B-B indicated in FIG. 1).

To form the gate cut trench 1400, an etching process 1401, which caninclude one or more stages, may be performed to remove a portion of thedummy gate 1004 and a portion of the dummy gate dielectric 1002 that aredisposed above the dummy fin 600A. Concurrently with forming the gatecut trench 1400, the same etching process may be performed to remove aportion of the dummy gate 1024 and a portion of the dummy gatedielectric 1022 that are disposed above the dummy fin 600B. During thefirst stage 1401, a mask 1403 may be formed over the dummy gatestructures 1000 and 1020 to expose respective portions of the dummygates 1004 and 1024 desired to be removed (e.g., the portion disposedover the dummy fins 600A-B), followed by the etching process. The mask1403 may be continued to be used during the following stages (if any) ofthe etching process.

In accordance with various embodiments, in the I/O area 302A, the gatecut trench 1400 may be formed to have a width (along the lengthwisedirection of the dummy gate structure 1000), W₁, which is approximatelyequal to the width 601A of the dummy fin 601A (as illustrated in FIGS.14A-B), or less than the width 601A of the dummy fin 601A (asillustrated in FIGS. 14C-D). In the core area, the gate cut trench 1450may be formed to have a width (along the lengthwise direction of thedummy gate structure 1020), W₂, which is approximately equal to thewidth 601B of the dummy fin 601B (as illustrated in FIGS. 14A-D).Whether the width W₁ of the gate cut trench 1400 in the I/O area 302A isequal to or less than the width 601A of the dummy fin 600A may bedetermined based on whether the width 601A is greater than a predefinedthreshold. For example, if the width 601A is greater than the threshold,the gate cut trench 1400 may be formed to have its width less than thewidth 601A (e.g., FIGS. 14C-D); and if the width 601A is less than orequal to the threshold, the gate cut trench 1400 may be formed to haveits width equal to the width 601A (e.g., FIGS. 14A-B). In certainprocess nodes (e.g., 5 nm), the threshold may be about 50 nm. However,it should be understood that the threshold can change according to theprocess nodes.

In some embodiments, each of the gate cut trenches 1400 and 1450 may beformed to have a non-tapered profile. For example in FIGS. 14A and 14C,the gate cut trenches 1400 and 1450 each have its sidewallsperpendicular to its bottom surface, e.g., the exposed top surfaces ofthe dummy fins 600A-B. As such, the width W₁ of the gate cut trench 1400may be defined as a distance globally separating the sidewalls of thegate cut trench 1400; and the width W₂ of the gate cut trench 1450 maybe defined as a distance globally separating the sidewalls of the gatecut trench 1450. In some other embodiments, each of the gate cuttrenches 1400 and 1450 may be formed to have a tapered profile. Forexample in FIGS. 14B and 14D, the gate cut trenches 1400 and 1450 eachhave its sidewalls connected to its bottom surface that has acurvature-based or edge-based profile. As such, the width W₁ of the gatecut trench 1400 may be defined as a distance separating the sidewalls ofthe gate cut trench 1400 that excludes the bottom surface; and the widthW₂ of the gate cut trench 1450 may be defined as a distance separatingthe sidewalls of the gate cut trench 1450 that excludes the bottomsurface.

Corresponding to operation 220 of FIG. 2, FIG. 15A is a cross-sectionalview of the FinFET device 300 including a gate isolation structure 1500in the I/O area 302A and a gate isolation structure 1550 in the corearea 302B at one of the various stages of fabrication. The gateisolation structures 1500 and 1550 shown in FIG. 15A are formed based onthe gate cut trenches 1400 and 1450 shown in FIG. 14A. FIGS. 15B, 15C,and 15D illustrate cross-sectional views of the FinFET device 300 inwhich the gate isolation structures 1500 and 1550 are formed based onthe gate cut trenches 1400 and 1450 shown in FIGS. 14B, 14C, and 14D,respectively. The cross-sectional views of FIGS. 15A-D are each cutalong the lengthwise direction of the dummy gate structures 1000 and1020 of the FinFET device 300 (e.g., cross-section B-B indicated in FIG.1).

The gate isolation structures 1500 and 1550 are formed by filling thegate cut trenches 1400 and 1450 (FIGS. 14A-D), respectively, with adielectric material. As such, the gate isolation structures 1500 and1550 can inherit the profiles (or dimensions) of the gate cut trenches1400 and 1450, respectively. For example in FIG. 15A, the gate isolationstructure 1500 can have a non-tapered profile, with the width W₁ that isabout equal to the width 601A of the dummy fin 600A, and the gateisolation structure 1550 can have a non-tapered profile, with the widthW₂ that is about equal to the width 601B of the dummy fin 600B. Forexample in FIG. 15B, the gate isolation structure 1500 can have atapered profile, with the width W₁ that is about equal to the width 601Aof the dummy fin 600A, and the gate isolation structure 1550 can have atapered profile, with the width W₂ that is about equal to the width 601Bof the dummy fin 600B. For example in FIG. 15C, the gate isolationstructure 1500 can have a non-tapered profile, with the width W₁ that isless than the width 601A of the dummy fin 600A, and the gate isolationstructure 1550 can have a non-tapered profile, with the width W₂ that isabout equal to the width 601B of the dummy fin 600B. For example in FIG.15D, the gate isolation structure 1500 can have a tapered profile, withthe width W₁ that is less than the width 601A of the dummy fin 600A, andthe gate isolation structure 1550 can have a tapered profile, with thewidth W₂ that is about equal to the width 601B of the dummy fin 600B.

The dielectric material that is used to form the gate isolationstructures 1500 and 1550 may include, for example, silicon oxide,silicon nitride, silicon oxynitride, silicon carbide, siliconcarbonitride, silicon oxycarbonitride, silicon oxycarbide, orcombinations thereof. The gate isolation structures 1500 and 1550 can beformed by depositing the dielectric material in the gate cut trenches1400 and 1450, respectively, using any suitable method, such as CVD,PECVD, or FCVD. After the deposition, a CMP may be performed to removeany excess dielectric material from the remaining dummy gate structures1000 and 1020.

Although the examples of FIGS. 15A-D show that the gate isolationstructures 1500 and 1550 respectively fill the gate cut trenches 1400and 1450 with a single dielectric piece (which can include one or moredielectric materials listed above), it is understood that the gateisolation structures 1500 and 1550 can each include multiple pieces.Each of the pieces may include, for example, silicon oxide, siliconnitride, silicon oxynitride, silicon carbide, silicon carbonitride,silicon oxycarbonitride, silicon oxycarbide, or combinations thereof.For example, the gate isolation structures 1500 and 1550 may eachinclude a first piece, which is formed as a conformal layer lining therespective gate cut trench, and a second piece, which fills the gate cuttrench with the first piece coupled therebetween. In another example,the gate isolation structures 1500 and 1550 may each include a firstpiece, which fills a lower portion of the respective gate cut trench,and a second piece, which fills an upper portion of the gate cut trench.

Corresponding to operation 222 of FIG. 2, FIG. 16A is a cross-sectionalview of the FinFET device 300 including an active gate structure 1600 inthe I/O area 302A and an active gate structure 1620 in the core area302B at one of the various stages of fabrication. The active gatestructures 1600 and 1620 shown in FIG. 16A are formed based on thecross-sectional view of the FinFET device 300 show in FIG. 15A. FIGS.16B, 16C, and 16D illustrate cross-sectional views of the FinFET device300 based on the cross-sectional views shown in FIGS. 15B, 15C, and 15D,respectively. The cross-sectional view of FIGS. 16A-D are each cut alongthe lengthwise direction of the active gate structures 1600 and 1620 ofthe FinFET device 300 (e.g., cross-section B-B indicated in FIG. 1).

The active gate structure 1600 may be formed by replacing the dummy gatestructure 1000 (FIGS. 15A-D); and the active gate structure 1620 may beformed by replacing the dummy gate structure 1020 (FIGS. 15A-D). Asillustrated, the active gate structure 1600 may include two portions1600A and 1600B that are separated by the gate isolation structure 1500and the dummy fin 600A; and the active gate structure 1620 may includetwo portions 1620A and 1620B that are separated by the gate isolationstructure 1550 and the dummy fin 600B. The portion 1600A can overlay theactive fin 404A; the portion 1600B can overlay the active fin 404B; theportion 1620A can overlay the active fin 404C; and the portion 1620B canoverlay the active fin 404D.

After the active gate structures 1600 and 1620 are formed, the FinFETdevice 300 can include a number of transistors. For example, a firstactive transistor, adopting the active fin 404A as its conductionchannel and portion 1600A as its active gate structure, may be formed; asecond active transistor, adopting the active fin 404B as its conductionchannel and portion 1600B as its active gate structure, may be formed; athird active transistor, adopting the active fin 404C as its conductionchannel and portion 1620A as its active gate structure, may be formed; afourth active transistor, adopting the active fin 404D as its conductionchannel and portion 1620B as its active gate structure, may be formed.Further, the first and second transistors, formed in the I/O area 302A,may be each configured as an I/O transistor; and the third and fourthtransistors, formed on the core area 302B, may be each configured as acore transistor.

The active gate structures 1600 and 1620 can each include a gatedielectric layer (e.g., 1602, 1622), a metal gate layer (1622, 1624),and one or more other layers that are not shown for clarity. Forexample, each of the active gate structures 1600 and 1620 may furtherinclude a capping layer and a glue layer. The capping layer can protectthe underlying work function layer from being oxidized. In someembodiments, the capping layer may be a silicon-containing layer, suchas a layer of silicon, a layer of silicon oxide, or a layer of siliconnitride. The glue layer can function as an adhesion layer between theunderlying layer and a subsequently formed gate electrode material(e.g., tungsten) over the glue layer. The glue layer may be formed of asuitable material, such as titanium nitride.

The gate dielectric layers 1602 and 1622 are each deposited (e.g.,conformally) in a corresponding gate trench to surround (e.g., straddle)one or more fins. For example in FIGS. 16A-D, the gate dielectric layerof the portion 1600A (sometimes referred to as “gate dielectric layer1602A”) is deposited in a gate trench that is formed by removing aportion of the dummy gate structure 1000 (e.g., the remaining dummy gatedielectric 1102 and dummy gate 1104) on the left-hand side of the dummyfin 600A. The gate dielectric layer 1602A can overlay the top surfacesand the sidewalls of the active fin 404A, one of the sidewalls of thedummy fin 600A, and one of the sidewalls of the gate isolation structure1500. The gate dielectric layer of the portion 1600B (sometimes referredto as “gate dielectric layer 1602B”) is deposited in a gate trench thatis formed by removing a portion of the dummy gate structure 1000 (e.g.,the remaining dummy gate dielectric 1002 and dummy gate 1004) on theright-hand side of the dummy fin 600A. The gate dielectric layer 1602Bcan overlay the top surfaces and the sidewalls of the active fin 404B,the other of the sidewalls of the dummy fin 600A, and the other of thesidewalls of the gate isolation structure 1500. The gate dielectriclayer of the portion 1620A (sometimes referred to as “gate dielectriclayer 1622A”) is deposited in a gate trench that is formed by removing aportion of the dummy gate structure 1020 (e.g., the remaining dummy gatedielectric 1022 and dummy gate 1024) on the left-hand side of the dummyfin 600B. The gate dielectric layer 1622A can overlay the top surfacesand the sidewalls of the active fin 404C, one of the sidewalls of thedummy fin 600B, and one of the sidewalls of the gate isolation structure1550. The gate dielectric layer of the portion 1620B (sometimes referredto as “gate dielectric layer 1622B”) is deposited in a gate trench thatis formed by removing a portion of the dummy gate structure 1020 (e.g.,the remaining dummy gate dielectric 1022 and dummy gate 1024) on theright-hand side of the dummy fin 600B. The gate dielectric layer 1622Bcan overlay the top surfaces and the sidewalls of the active fin 404D,the other of the sidewalls of the dummy fin 600B, and the other of thesidewalls of the gate isolation structure 1550.

The gate dielectric layers 1602 and 1622 each include silicon oxide,silicon nitride, or multilayers thereof. In example embodiments, thegate dielectric layers 1602 and 1622 each include a high-k dielectricmaterial, and in these embodiments, the gate dielectric layers 1602 and1622 may each have a k value greater than about 7.0, and may include ametal oxide or a silicate of Hf, Al, Zr, La, Mg, Ba, Ti, Pb, orcombinations thereof. The formation methods of the gate dielectriclayers 1602 and 1622 may include molecular beam deposition (MBD), atomiclayer deposition (ALD), PECVD, and the like. A thickness of each of thegate dielectric layers 1602 and 1622 may be between about 8 angstroms(Å) and about 20 Å, as an example.

The metal gate layers 1604 and 1627 may each be formed over therespective gate dielectric layer. The metal gate layer of the portion1600A (sometimes referred to as “metal gate layer 1604A”) is depositedin the gate trench over the gate dielectric layer 1602A; the metal gatelayer of the portion 1600B (sometimes referred to as “metal gate layer1604B”) is deposited in the gate trench over the gate dielectric layer1602B; the metal gate layer of the portion 1620A (sometimes referred toas “metal gate layer 1624A”) is deposited in the gate trench over thegate dielectric layer 1622A; and the metal gate layer of the portion1620B (sometimes referred to as “metal gate layer 1624B”) is depositedin the gate trench over the gate dielectric layer 1622B.

The metal gate layers 1604 and 1624 may each be a P-type work functionlayer, an N-type work function layer, multi-layers thereof, orcombinations thereof, in some embodiments. Accordingly, the metal gatelayers 1604 and 1624 may each be referred to as a work function layer,in some embodiments. In the discussion herein, a work function layer mayalso be referred to as a work function metal. Example P-type workfunction metals that may be included in the gate structures for P-typedevices include TiN, TaN, Ru, Mo, Al, WN, ZrSi₂, MoSi₂, TaSi₂, NiSi₂,WN, other suitable P-type work function materials, or combinationsthereof. Example N-type work function metals that may be included in thegate structures for N-type devices include Ti, Ag, TaAl, TaAlC, TiAlN,TaC, TaCN, TaSiN, Mn, Zr, other suitable N-type work function materials,or combinations thereof.

A work function value is associated with the material composition of thework function layer, and thus, the material of the work function layeris chosen to tune its work function value so that a target thresholdvoltage V_(t) is achieved in the device that is to be formed. The workfunction layer(s) may be deposited by CVD, physical vapor deposition(PVD), ALD, and/or other suitable process. The thickness of a P-typework function layer may be between about 8 Å and about 15 Å, and thethickness of an N-type work function layer may be between about 15 Å andabout 30 Å, as an example.

FIGS. 17A, 17B, and 17C each illustrate a top view of a portion of theFinFET device 300 after the active gate structures 1600 and/or 1620 areformed, in accordance with various embodiments. For example, FIG. 17Aillustrates the top view of the portion of the FinFET device 300 in thecore area 302B. As shown, the gate isolation structure 1550 separatesthe active gate structure 1620 into two portions that overlay the activefins 404C and 404D, respectively. When viewed from the top, the gateisolation structure 1550 has the width W₂ (along the lengthwisedirection of the active gate structure 1620) that is about equal to thewidth 601B of the dummy fin 600B that is disposed between the activefins 404C and 404D. FIG. 17B illustrates the top view of the portion ofthe FinFET device 300 in the I/O area 302A, when the width 601A of thedummy fin 600A is less than or equal to a predefined threshold. Asshown, the gate isolation structure 1500 separates the active gatestructure 1600 into two portions that overlay the active fins 404A and404B, respectively. When viewed from the top, the gate isolationstructure 1500 has the width W₁ (along the lengthwise direction of theactive gate structure 1600) that is about equal to the width 601A of thedummy fin 600A that is disposed between the active fins 404A and 404B.FIG. 17C illustrates the top view of the portion of the FinFET device300 in the I/O area 302A, when the width 601A of the dummy fin 600A isgreater than the predefined threshold. As shown, the gate isolationstructure 1500 separates the active gate structure 1600 into twoportions that overlay the active fins 404A and 404B, respectively. Whenviewed from the top, the gate isolation structure 1500 has the width W₁(along the lengthwise direction of the active gate structure 1600) thatis less than the width 601A of the dummy fin 600A that is disposedbetween the active fins 404A and 404B. As further illustrated in FIGS.17A-C, each of the dummy fins (e.g., 600A, 600B) is spaced apart fromthe adjacent active fins (e.g., 404A, 404B, 404C, 404D) by a distance,“d,” that ranges from about 20 angstroms to about 500 angstroms.

In one aspect of the present disclosure, a semiconductor device isdisclosed. The semiconductor device includes a substrate including afirst area and a second area. A first density of transistors formed inthe first area is greater than a second density of transistors formed inthe second area. The semiconductor device in the first area includes: afirst semiconductor fin and a second semiconductor fin, both the firstand second semiconductor fins extending along a first direction; a firstdielectric fin that extends along the first direction and is disposedbetween the first and second semiconductor fins, wherein the firstdielectric fin has sidewalls separated by a first distance along asecond direction perpendicular to the first direction; and a first gateisolation structure vertically disposed above the first dielectric fin,wherein the first gate isolation structure has sidewalls separated by asecond distance along the second direction, and wherein the firstdistance is equal to the second distance. The semiconductor device inthe second area includes: a third semiconductor fin and a fourthsemiconductor fin, both the third and fourth semiconductor finsextending along the first direction; a second dielectric fin thatextends along the first direction and is disposed between the third andsecond fourth fins, wherein the second dielectric fin has sidewallsseparated by a third distance along the second direction; and a secondgate isolation structure vertically disposed above the second dielectricfin, wherein the second gate isolation structure has sidewalls separatedby a fourth distance along the second direction, and wherein the fourthdistance is less than the third distance.

In another aspect of the present disclosure, a semiconductor device isdisclosed. The semiconductor device includes a first plurality oftransistors, and a second plurality of transistors. The first pluralityof transistors are configured to operate under a lower gate voltage thanthe second plurality of transistors. The first plurality of transistorsinclude a first transistor having a first active gate structure and asecond transistor having a second active gate structure. The first andsecond active gate structures are separated from each other by a firstdielectric fin and a first gate isolation structure along a firstdirection, the first dielectric fin having a first width along the firstdirection, the first gate isolation structure having a second widthalong the first direction, the first width being equal to the secondwidth. The second plurality of transistors includes a third transistorhaving a third active gate structure and a fourth transistor having afourth active gate structure. The third and fourth active gatestructures are separated from each other by a second dielectric fin anda second gate isolation structure along the first direction, the seconddielectric fin having a third width along the first direction, thesecond gate isolation structure having a fourth width along the firstdirection, the third width being greater than the fourth width.

In yet another aspect of the present disclosure, a method for making asemiconductor device is disclosed. The method includes forming a firstsemiconductor fin and a second semiconductor fin over a substrate thatboth extend along a first direction. The method includes forming adielectric fin that extends along the first direction and is disposedbetween the first and second semiconductor fins. The dielectric fin hasa first width along a second direction perpendicular to the firstdirection. The method includes forming a dummy gate structure thatextends along the second direction and straddles the first and secondsemiconductor fins and the dielectric fin. The method includesdetermining that the first width is greater than a predefined threshold.The method includes removing a portion of the dummy gate structure overthe dielectric fin to form a trench that has a second width along thesecond direction. The second width is less than the first width. Themethod includes filling the trench with a dielectric material.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A semiconductor device, comprising: a substrateincluding a first area and a second area, wherein a first density oftransistors formed in the first area is greater than a second density oftransistors formed in the second area; wherein the semiconductor devicein the first area comprises: a first semiconductor fin and a secondsemiconductor fin, both the first and second semiconductor finsextending along a first direction; a first dielectric fin that extendsalong the first direction and is disposed between the first and secondsemiconductor fins, wherein the first dielectric fin has sidewallsseparated by a first distance along a second direction perpendicular tothe first direction; and a first gate isolation structure verticallydisposed above the first dielectric fin, wherein the first gateisolation structure has sidewalls separated by a second distance alongthe second direction, and wherein the first distance is equal to thesecond distance; and wherein the semiconductor device in the second areacomprises: a third semiconductor fin and a fourth semiconductor fin,both the third and fourth semiconductor fins extending along the firstdirection; a second dielectric fin that extends along the firstdirection and is disposed between the third and second fourth fins,wherein the second dielectric fin has sidewalls separated by a thirddistance along the second direction; and a second gate isolationstructure vertically disposed above the second dielectric fin, whereinthe second gate isolation structure has sidewalls separated by a fourthdistance along the second direction, and wherein the fourth distance isless than the third distance.
 2. The semiconductor device of claim 1, inthe first area, further comprising a first metal gate layer extendingalong the second direction, wherein the first metal gate layer includesa first portion straddling the first semiconductor fin and a secondportion straddling the second semiconductor fin.
 3. The semiconductordevice of claim 1, in the second area, further comprising a second metalgate layer extending along the second direction, wherein the secondmetal gate layer includes a first portion straddling the thirdsemiconductor fin and a second portion straddling the fourthsemiconductor fin.
 4. The semiconductor device of claim 1, wherein thethird distance is greater than the first distance.
 5. The semiconductordevice of claim 1, wherein the first semiconductor fin and the secondsemiconductor fin are configured as respective active channels of afirst transistor and a second transistor in the first area and the firstdielectric fin is configured as a dummy channel in the first area. 6.The semiconductor device of claim 5, wherein the third semiconductor finand the fourth semiconductor fin are configured as respective activechannels of a third transistor and a fourth transistor in the secondarea and the second dielectric fin is configured as a dummy channel inthe second area.
 7. The semiconductor device of claim 6, wherein thefirst and second transistors are configured for operation under a firstgate voltage, and the third and fourth transistors are configured foroperation under a second gate voltage, and wherein the second gatevoltage is greater than the first gate voltage.
 8. A semiconductordevice, comprising: a first plurality of transistors; and a secondplurality of transistors, the first plurality of transistors configuredto operate under a lower gate voltage than the second plurality oftransistors; wherein the first plurality of transistors comprise a firsttransistor having a first active gate structure and a second transistorhaving a second active gate structure; wherein the first and secondactive gate structures are separated from each other by a firstdielectric fin and a first gate isolation structure along a firstdirection, the first dielectric fin having a first width along the firstdirection, the first gate isolation structure having a second widthalong the first direction, the first width being equal to the secondwidth; wherein the second plurality of transistors comprise a thirdtransistor having a third active gate structure and a fourth transistorhaving a fourth active gate structure; and wherein the third and fourthactive gate structures are separated from each other by a seconddielectric fin and a second gate isolation structure along the firstdirection, the second dielectric fin having a third width along thefirst direction, the second gate isolation structure having a fourthwidth along the first direction, the third width being greater than thefourth width.
 9. The semiconductor device of claim 8, wherein the secondplurality of transistors comprise a fifth transistor having a fifthactive gate structure and a sixth transistor having a sixth active gatestructure, and wherein the fifth and sixth active gate structures areseparated from each other by a third dielectric fin and a third gateisolation structure along the first direction, the third dummy finhaving a fifth width along the first direction, the third gate isolationstructure having a sixth width along the first direction, the fifthwidth being equal to the sixth width.
 10. The semiconductor device ofclaim 8, wherein the first transistor includes a first semiconductor finextending along a second direction perpendicular to the first directionand the second transistor includes a second semiconductor fin extendingalong the second direction, and wherein the first dielectric fin thatalso extends along the second direction is disposed between the firstand second semiconductor fins.
 11. The semiconductor device of claim 10,wherein the first active gate structure straddles the firstsemiconductor fin and the second active gate structure straddles thesecond semiconductor fin, and wherein the first and second active gatestructures extend along the first direction.
 12. The semiconductordevice of claim 8, wherein the third transistor includes a thirdsemiconductor fin extending along a second direction perpendicular tothe first direction and the fourth transistor includes a fourthsemiconductor fin extending along the second direction, and wherein thesecond dielectric fin that also extends along the second direction isdisposed between the third and fourth semiconductor fins.
 13. Thesemiconductor device of claim 12, wherein the third active gatestructure straddles the third semiconductor fin and the fourth activegate structure straddles the third semiconductor fin, and wherein thethird and fourth active gate structures extend along the firstdirection.
 14. The semiconductor device of claim 8, wherein the firstplurality of transistors and the second plurality of transistors aredisposed in a first area and a second area of a substrate, respectively,and wherein a first density of transistors formed in the first area isgreater than a second density of transistors formed in the second area.15. The semiconductor device of claim 8, wherein the third distance isgreater than the first distance.
 16. A method of making a semiconductordevice, comprising: forming a first semiconductor fin and a secondsemiconductor fin over a substrate that both extend along a firstdirection; forming a dielectric fin that extends along the firstdirection and is disposed between the first and second semiconductorfins, wherein the dielectric fin has a first width along a seconddirection perpendicular to the first direction; forming a dummy gatestructure that extends along the second direction and straddles thefirst and second semiconductor fins and the dielectric fin; determiningthat the first width is greater than a predefined threshold; removing aportion of the dummy gate structure over the dielectric fin to form atrench that has a second width along the second direction, wherein thesecond width is less than the first width; and filling the trench with adielectric material.
 17. The method of claim 16, further comprisingdetermining that the first width is less than or equal to the predefinedthreshold to form the trench that has a third width along the seconddirection, wherein the third width is equal to the first width.
 18. Themethod of claim 16, wherein the predefined threshold is about 50nanometers.
 19. The method of claim 16, further comprising replacing thedummy gate structure with an active gate structure that includesportions overlaying the first semiconductor fin and the secondsemiconductor fin, respectively, thereby forming a first transistor anda second transistor.
 20. The method of claim 19, wherein the firsttransistor and the second transistor are disposed in an input/outputarea over the substrate.